1. Field of the Invention
The present invention is directed to a turbine wheel arrangement and an impeller wheel arrangement for a hydrodynamic torque converter comprising an outer shell connected with a respective hub for common rotation and a plurality of vanes or blades arranged successively in the circumferential direction at the outer shell. The blades are connected to an inner shell at a side of the blades remote from the outer shell. Fluid flow channels are formed between the successive of blades and in the outer shell and inner shell.
2. Description of the Related Art
Prior art impeller wheel arrangements and turbine wheel arrangements having blades arranged successively along a circumferential direction are used in known torque converters and have the problem that the blade configuration, i.e., the contouring of the blades must be adapted to different operating ranges or operating points of a torque converter to provide the respective fluid flow channels to provide operating characteristics that are acceptable over a relatively large operating range and a good torque transmission and so that the torque converter has a relatively high efficiency. For example, at the starting operating point of a vehicle a high staring conversion is required in which the turbine wheel arrangement essentially does not rotate and initially only the impeller wheel arrangement is driven by the driving means, whereas at an operating point of a vehicle where the ratio of the speed of the turbine wheel arrangement to the speed of the impeller wheel arrangement is greater than 0.8 a high efficiency is required. To completely satisfy each of these operating requirements, the blades of the turbine wheel arrangement and/or of the impeller wheel arrangement would have to be constructed with different blade contours. Since only one blade contour is possible in each device, compromises were made in the prior art devices with regard to the blade contouring for different operating points to provide an acceptable converter characteristic for the starting range as well as for the normal or approximately constant driving range. It is obvious that, based on this compromise, no approximately optimum converter characteristic can be provided in any of the relevant driving ranges.
A prior torque converter is disclosed in European Patent EP 0 846 893 A2 in which the respective blades in both turbine and impeller are constructed so as to be completely offset along a direction of flow, i.e., blade portions lying in different areas in the circumferential direction are provided. An arrangement of this type is intended to prevent separation of flow in modem torque conveners which, owing to a lack of sufficient installation space, are constructed in an axially flat manner. This is achieved by offsetting the two blade portions relative to one another at the translational area between the two blade portions. The translational area is constructed in a stopped manner and extends along the flow direction. However, no additional adapting measures are taken in this torque converter of the prior art in the area of the impeller wheel or turbine wheel which would make them especially suitable for determined operating states or for a greater range of operating states.